1. Field of the Invention
The present invention relates to an improvement in a heat pump apparatus of a type using nonazeotropic mixed refrigerant and capable of varying its composition by reserving high boiling point refrigerant through the separation of composition.
We have disclosed in apparatus as shown in FIG. 9 arranged to use nonazeotropic mixed refrigerant and capable of varying its composition by retaining high boiling point refrigerant through the separation of composition. Referring to FIG. 9, reference numeral 1 represents a compressor, 2 represents a condenser, 3 represents a main restrictor, and 4 represents an evaporator. The main circuit of the heater apparatus is formed by connecting the above-described elements. Reference numeral 5 represents a fractioning/separating device filled with filler, the fractioning/separating device 5 having the upper portion connected to an outlet port of the condenser 2 via a pipe 6 and also connected to an inlet port of the evaporator 4 via an auxiliary restrictor 7. A reservoir 8 is disposed below the fractioning/separating device 5, the bottom of the reservoir 8 being connected to the auxiliary restrictor 7 via a valve 9. Furthermore, a heater 10 is disposed in reservoir 8.
Then, the method of varying the composition of enclosed nonazeotropic mixed refrigerant will be described. In the case where the apparatus is operated with the composition of the enclosed mixed-refrigerant being retained as it is (in non-separation mode), the operation of the heater 10 is stopped. In this case, the reservoir 8 acts to only retain excess refrigerant in such a manner that it retains the excess refrigerant when the valve 9 is closed while it retains the same, and as well discharges a portion of refrigerant to the evaporator 4 via the auxiliary restrictor 7 when the valve 9 is opened, causing no change in the composition to take place. Therefore, the main circuit is caused to be operated while maintaining the composition of the enclosed mixed-refrigerant enriched with high boiling point refrigerant.
On the other hand, in the case where the apparatus is operated with refrigerant of the composition enriched with low boiling point refrigerant while retaining high boiling point refrigerant (in a separation mode), the low boiling point refrigerant in the refrigerant in the reservoir 8 is mainly evaporated, the evaporated low boiling point refrigerant then moving upwards through the fractioning/separating device 5 when the valve 9 is closed and the heater 10 is operated. At this time, liquid refrigerant is supplied from the outlet port of the condenser 2 via the pipe 6 so that fraction takes place in the fractioning/separating device 5 due to a gas-liquid contact. As a result, the density of the low boiling point refrigerant in the gas which is moving upwards is raised, while the density of the high boiling point refrigerant in the liquid moving downwards, is raised. As a result, high boiling point refrigerant in the form of a condensed liquid is retained in the reservoir 8. On the other hand, the gas which is moving upwards and enriched with low boiling point refrigerant is introduced into the evaporator 4 via the auxiliary restrictor 7. Therefore, the main circuit can be operated while maintaining the composition enriched with the low boiling point refrigerant.
In the case that the heat pump apparatus of the above-described type which is capable of varying the composition is used, for example, in a hot water supply apparatus in which when hot water is intended to be obtained, the apparatus is operated while maintaining the enclosed composition enriched with high boiling point refrigerant whose condensing pressure is low so as to improve the reliability of the compressor or the like. When hot water is reserved in a short time by utilizing high heating performance, the apparatus can be operated while maintaining the composition enriched with low boiling point refrigerant which exhibits excellent heating performance.
However, since the heat pump apparatus of the type described above is operated with the pressure of its fractioning/separating device which is as high as the pressure in the main circuit, the separating performance of the fractioning/separating device has been insufficient. That is, it has been known that the performance of the fractioning/separating device can be improved by raising the velocity of the gas which moves upwards in the fractioning/separating device. If separation is conducted at high pressure as described above, the specific volume of the gas generated in the reservoir due to heat applied from the heater is reduced, causing the velocity of the gas in the fractioning/separating device to be reduced. Therefore, the apparatus of the type described above suffers from insufficient separating performance. In order to overcome the insufficient separating performance, the quantity of heat of the heater has been increased in the conventional apparatus. It leads to the reduction in the coefficient of performance. Furthermore, if separation is conducted at high pressure, the saturated temperature of the refrigerant in the reservoir is raised excessively, causing problems in terms of the heat resistance of the devices and unnecessary heat radiation to occur.